In the discussion that follows, reference is made to certain structures and/or methods. However, the following references should not be construed as an admission that these structures and/or methods constitute prior art. Applicant expressly reserves the right to demonstrate that such structures and/or methods do not qualify as prior art against the present invention.
Drills of the above-related kind, which belong to the category of short hole drills, and which, as a consequence of the shape of the chip flutes, commonly are denominated twist drills, are used to recess holes by cutting or chip removing machining in workpieces of metal, such as steel, aluminium, cast iron, etc. The drills may also be used for hole making in different forms of composite material.
Of great importance to the quality of the completed hole in respect of dimensional accuracy and surface smoothness is the formation and evacuation, respectively, of the chips. Namely, if the chips tend to be pressed out towards the generated hole wall, its surface quality is deteriorated. In severe cases, the chips may entangle each other and cause chip jammings, which in the worst case may lead to tool breakdown as well as rejection of the workpiece. Thus, there is a general aim to construct the drills so that a flexible chip evacuation is guaranteed. Another aim is to provide drills that are easy-cutting not only with the purpose of guaranteeing good hole quality, but also of reducing the energy consumption and the time required for the hole-making operation.